Three-dimensional diagnostic images of the brain, spinal cord, and other body portions are produced by diagnostic imaging equipment such as CT scanners, magnetic resonance imagers, and the like. These imaging modalities often provide structural detail with a resolution of a millimeter or better.
Image guided surgery systems have been developed to utilize this data to assist the surgeon in presurgical planning and in accurately locating a region of interest within the body of a patient. In the operating arena, the image guided surgery systems are used to display position and orientation of a surgical tool in its correct location with respect to the images of the patient. One example of an image guided surgery system is U.S. Pat. No. 5,517,990, Stereotaxy Wand and Tool Guide, to Kalfas et al. issued May 21, 1996, incorporated by reference herein.
In order to further aid the surgeon in viewing an area of interest within the patient's body, a high powered surgical microscope is often utilized. Such a microscope may, for instance, be used to see blood vessels or other microscopic details within the patient. The microscope is supported by a movable electronic support structure which may be rolled along the ground or mounted to a ceiling or a wall, for example. Controls adjacent the microscope on the support structure allow the surgeon to manually or electronically position the microscope over the patient's body at a desired location.
In order to track the location of the microscope within the surgical room or other area, a series of position signaling devices such as infrared emitters or reflectors are typically secured to the microscope at some location. The position signaling devices are tracked by a localizer located within the surgical room capable of sensing the position signaling devices. The image guided surgery system uses this data to provide the surgeon with an indication of the position and orientation of the microscope with respect to patient data and images. Such precise tracking of the microscope is helpful to ensure the surgeon knows in exactly what direction the microscope should be moved to see an area of interest.
Unfortunately, calibrating or determining attributes of a microscope such that a viewing area of the microscope is properly tracked with respect to images displayed on a monitor is often a nuisance. For instance, each time the microscope is accidently bumped or otherwise shaken the microscope attributes typically needs to be re-calibrated. This is true in part because upon being bumped the position indicators attached to the microscope are also often moved or dislocated. Because the microscope is tracked with respect to the location of the position indicators, such movement causes errors in tracking which can lead the surgeon to focus on an incorrect location within a patient. Further, if the microscope is bumped or jarred during a surgical procedure, the surgeon may need to take time away from the procedure to re-calibrate the microscope.
The present invention provides a new and improved method and apparatus for calibrating and verifying calibration of various attributes of a surgical microscope which addresses the above-referenced matters, and others.